JavaScriptCore-7600.1.4.9.tar.gz

[apple/javascriptcore.git] / dfg / DFGStoreBarrierElisionPhase.cpp

diff --git a/dfg/DFGStoreBarrierElisionPhase.cpp b/dfg/DFGStoreBarrierElisionPhase.cpp
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+/*
+ * Copyright (C) 2013 Apple Inc. All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions
+ * are met:
+ * 1. Redistributions of source code must retain the above copyright
+ *    notice, this list of conditions and the following disclaimer.
+ * 2. Redistributions in binary form must reproduce the above copyright
+ *    notice, this list of conditions and the following disclaimer in the
+ *    documentation and/or other materials provided with the distribution.
+ *
+ * THIS SOFTWARE IS PROVIDED BY APPLE INC. AND ITS CONTRIBUTORS ``AS IS''
+ * AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO,
+ * THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
+ * PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL APPLE INC. OR ITS CONTRIBUTORS
+ * BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
+ * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
+ * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
+ * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
+ * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
+ * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF
+ * THE POSSIBILITY OF SUCH DAMAGE.
+ */
+
+#include "config.h"
+#include "DFGStoreBarrierElisionPhase.h"
+
+#if ENABLE(DFG_JIT)
+
+#include "DFGBasicBlock.h"
+#include "DFGClobberize.h"
+#include "DFGGraph.h"
+#include "DFGPhase.h"
+#include "JSCInlines.h"
+#include <wtf/HashSet.h>
+
+namespace JSC { namespace DFG {
+
+class StoreBarrierElisionPhase : public Phase {
+public:
+    StoreBarrierElisionPhase(Graph& graph)
+        : Phase(graph, "store barrier elision")
+        , m_currentBlock(0)
+        , m_currentIndex(0)
+    {
+    }
+
+    bool run()
+    {
+        for (BlockIndex blockIndex = 0; blockIndex < m_graph.numBlocks(); ++blockIndex) {
+            m_currentBlock = m_graph.block(blockIndex);
+            if (!m_currentBlock)
+                continue;
+            handleBlock(m_currentBlock);
+        }
+        return true;
+    }
+
+private:
+    bool couldCauseGC(Node* node)
+    {
+        return writesOverlap(m_graph, node, GCState);
+    }
+
+    bool allocatesFreshObject(Node* node)
+    {
+        switch (node->op()) {
+        case NewObject:
+        case NewArray:
+        case NewArrayWithSize:
+        case NewArrayBuffer:
+        case NewTypedArray:
+        case NewRegexp:
+            return true;
+        default:
+            return false;
+        }
+    }
+
+    void noticeFreshObject(HashSet<Node*>& dontNeedBarriers, Node* node)
+    {
+        ASSERT(allocatesFreshObject(node));
+        dontNeedBarriers.add(node);
+    }
+
+    Node* getBaseOfStore(Node* barrierNode)
+    {
+        ASSERT(barrierNode->isStoreBarrier());
+        return barrierNode->child1().node();
+    }
+
+    bool shouldBeElided(HashSet<Node*>& dontNeedBarriers, Node* node)
+    {
+        ASSERT(node->isStoreBarrier());
+        return dontNeedBarriers.contains(node->child1().node());
+    }
+
+    void elideBarrier(Node* node)
+    {
+        ASSERT(node->isStoreBarrier());
+        node->convertToPhantom();
+    }
+
+    void handleNode(HashSet<Node*>& dontNeedBarriers, Node* node)
+    {
+        if (couldCauseGC(node))
+            dontNeedBarriers.clear();
+
+        if (allocatesFreshObject(node))
+            noticeFreshObject(dontNeedBarriers, node);
+
+        if (!node->isStoreBarrier())
+            return;
+
+        if (shouldBeElided(dontNeedBarriers, node)) {
+            elideBarrier(node);
+            return;
+        }
+
+        Node* base = getBaseOfStore(node);
+        if (!base)
+            return;
+
+        if (dontNeedBarriers.contains(base))
+            return;
+        dontNeedBarriers.add(base);
+    }
+
+    bool handleBlock(BasicBlock* block)
+    {
+        HashSet<Node*> dontNeedBarriers;
+        for (unsigned indexInBlock = 0; indexInBlock < block->size(); ++indexInBlock) {
+            m_currentIndex = indexInBlock;
+            Node* node = block->at(indexInBlock);
+            handleNode(dontNeedBarriers, node);
+        }
+        return true;
+    }
+
+    BasicBlock* m_currentBlock;
+    unsigned m_currentIndex;
+};
+    
+bool performStoreBarrierElision(Graph& graph)
+{
+    SamplingRegion samplingRegion("DFG Store Barrier Elision Phase");
+    return runPhase<StoreBarrierElisionPhase>(graph);
+}
+
+
+} } // namespace JSC::DFG
+
+#endif // ENABLE(DFG_JIT)